One way of analyzing a fluid such as blood or serum is to draw the fluid into an element such as an inert container in a predetermined amount and subsequently to divide this sample into accurately determined sections which are discharged into other containers. Such analyzing tecniques depend to a very great extent upon the drawing of the correct amount of the fluid being analyzed into an additional container and the dispensing of the same into, for example, a new diluent.
Methods for drawing up fluids or pipetting the same are shown, for exampe, in earlier U.S. Pat. Nos. 3,244,324; 3,665,980; and in my earlier copending application Ser. No. 307,360, filed Nov. 17, 1972 which has already been allowed.
In U.S. Pat. No. 3,244,324 is disclosed a pipetting apparatus including an inlet conduit adapted for the supply of fluid with a chamber being arranged approximate the inlet conduit. The chamber is in the form of a tube having a bore of predetermined size and having two oppositely disposed ends. A scale device is operatively associated with the chamber intermediate the aforementioned ends and a first cap member is provided on one end of the tube sealing the same. A free piston is provided in the tube and has a size corresponding to that of the bore, the piston being slidable in the bore and dividing the chamber into two sections in substantially fluid tight manner. An adjustment means is provided on and seals the other end of the tube and includes a stop within the chamber which is adjustable relative to the scale means. An outlet conduit is coupled by two further conduits to the aforementioned tube proximate the ends of the same. As can be seen from the drawing of this patent, the apparatus provided is a volumetric dispensing apparatus which is not portable nor manually manipulable nor is any special provision made for the thorough purging of the bore in which the fluid is accumulated and subsequently dispensed.
Patents relating to the subject matter of U.S. Pat. No. 3,244,324 include the following U.S. Pat. Nos: 813,977; 1,188,085; 1,280,481; 1,784,892; 2,158,102; 2,406,239; 2,559,317; 2,576,747; 2,869,575; 3,138,290 and 3,138,294. These patents do not take care of the matters specifically raised hereinabove.
U.S. Pat. No. 3,665,980 describes a more sophisticated type of apparatus involving electronic control circuits. In this patent is disclosed a dispensing apparatus having various modes of operation including automatic, manual and prime modes. The dispensing apparatus includes coarse and fine metering devices consisting of cylinders with pistons displaceable therein. The displacement of the pistons is controlled by adjustable switches. The metering devices are associated with dispensing nozzles beneath which a tray is incrementally moved in which are receptacles for vials and the like. Although this apparatus provides for a priming mode, there is no particular arrangement made for thoroughly purging needed amounts of fluid from the cylinders in which these amounts are collected.
Other patents relating to this last mentioned structure include the following U.S. Pat. Nos: 1,739,252; 2,220,707; 2,658,644; 3,275,042; 3,364,759; 3,447,576; 3,525,592 and 3,536,449. These patents similarly do not deal with the limitations of the aforementioned structure.
Finally, my earlier copending application Ser. No. 307,360 discloses a pipette provided with an adjustable dispensing volume and with a control which makes the selected volume effective for repeated dispensing operations or for a one shot operation. A glass vial is associated with intake and dispensing valves and a piston is inserted therein. The vial or tube is encircled by a sheath connected with the piston and having a flange engaged by an adjustable stop which engages a flange on the sheath and limits the withdrawal of the piston from the tube and hence the fluid intake. It therefore limits the amount of fluid dispensed on the next sequential movement of the piston into the tube. This apparatus is however not particularly portable and no special provision is made for purging the receptacle into which the metered fluid is withdrawn during the next discharging operation.
The patents mentioned as having relevance to the last mentioned structure include the following U.S. Pat. Nos: 2,096,461; 2,198,666; 3,337,096, 2,548,752 and 2,605,019.